Thermionic tube



Sept. 7 1926. 1,599,180-

o. T. Mcn vAnNE THERMIONIC TUBE Filed July 2 1925 0.2". Mcfzvafm.

Attorneys,

Patented Sept. 7, 1926,.

UNITED STATES" y 1,599,180 P'.^.Tr.1-1rl oFFlcE.

ORAN T. HcILVAINE, OF EAST CLEVELAND, OHIO, ASSIGNOR TO THE RADIO TELE- VISION COMPANY, OF CLEVELAND, OHIO, A. CORPORATION OF OHIO.

.THERMONIC TUBE.

This invention relates to thcrmionic tubes such as are employed in the transmission, reception, detection, and amphficatlon of soumis and signals as in Wireless, radio, telephone, announcers, rectiiers, and the like and has for its object the provision ot' new and vimproved expedients for producing a uniform and reliable electroni-c emission by the use ot' alternating current, thereby dispensing with the battery hitherto usually employed for the purpose. Another object.

of the invention is the provision of a thcrmionic tube wherein the electronic emission is produced by the use of alternating current, the operative parts being so arranged and so shielded from local static influence as to enable the omission of any special biasing battery; the provision of an alternating current tube which can be used in standard radio sets with av minimum of rearrange ment; While further objects and advantages of the invention will become apparent as the description proceeds.

In the drawings accompanying and forming a part of this application Fig. 1 is a. central'sectional View through a radio tube of conventional design the same being equipped `with my improvements; Fig. 2 is a top plan vievv of the elements shown in Fig. 1; and Fig. 3 is a sectional view through an emissiontube containing my improvements, certain of the arrangements being` slightly modified from that shown in Fig. 1.

My invention comprises the use of a closed impervious tube I'preferably made of metal and `hermetically sealed in the Wall of they vacuum chamber, the interior of the tube v containing the heat producing device and the exterior of the tube .carrying the electron emission provisions. In the simplest and most approved form this tube is either directly or indirectly sealed into or otherwise joined to-the press 2 which constitutes the closure for the base of the glass globe 3, and this press also may conveniently carry any other operating elements which the tube contains, such as the grid Which is here illustrated as consisting of a loop of iine Wires 4 wound on posts 5, 5, carried by the press; and the plate 6,l here shown asa sheet of metal supported by other posts 7 7, also carried by the press outside of the first posts. Ordinarily the base of the tube is completed by a cap 8 of some convenient or suitable material provided with suitable insulated terminal posts, certain of whichI are indicated at i) and 10 respectively. In Fig. l l have shown the contact 9 as connected to the grid and the Contact 10 as connected to the tube l. the plate having a conductor 1l leading therefrom to another contact (not shown). f f

vMounted inside. the tube 1 is a suitable' heating element which may be of any suitable or desired construction but preferably cznnprises a resistance wire l2 of nickel steel7 nickel chromium or other suitable alloy wound and generally submerged in or embraced by some kind of electrical insulating material l having as high a conductivity for heat as is compatible with the desired electrical properties. This ,heating element may either he permanently mounted in the tube 1 or removably supported therein, in which latter case it is ot' course replaceable. in the event of failure or burning out. In case the element lis replaceable the 'tube base is preferably provided With a remov- .able plug 144 as shown in Fig. 1 in order to enable ready access. The resistance element is connected to wires 15 leading to this plug, which may constitute one part 'of a separable connector, the other part 16 of which is connected to the flexible lead Wires 17.

The heating element may be. designed for any desired voltage, and this voltage may in turn have some effect upon the construction of the rest of the tube. According to one mode. of construction the heating element is made with comparatively large and short resistorsA and is connected to the alternat-ing current through a .step-down transformer 18 as shown in Fig. 1, whereby the'- voltage in the heating element is reduced. This has several advantages, one of Which is that the electrostatic effect of the current is likewise made so small as to be less obnoxious. The exterior of the tube is preferably treated or'coated with a layer of some material having a high emissivecapacity at comparatively low temperature, such as the oxides of barium, strontium, thorium.,

etc., and the exterior portion of this tube is made of electric conducting material conneet-ed by means of the Wire 16 to one of the tube contacts as 10. In the simplest construction the. entire tube 1 is made o' meta-l, some metal-ot course being used which can be sealed to the glass, although it is equally y Within my invention to employ a hard glass tube having a metallic covering to which this Wire is attached.

According to another form of my invention a metal sleeve 20 is used as the emitting member, being coated exteriorly with a layer 21 of high emissive material, and suitably connected by the wire 16 to the proper terminal. Intcriorly this sleeve is 'insulated from the tube 1 by means of a layer 22 of some material having a high degree of electrical insulation coupled with the highest possible degree of heat conductivity such as mica, enamel, porcelain, etc., the tube l being grounded by way of a suitable conductor 24. This arrangement is particularly desirable in case the tube is designed for direct connection to a 110 volt lighting circuit, since the interposition of this grounded member between the resistor and the tube interior shields the latter from electrostatic effect. Of course this arrangement is not limited to use with high potential, but is particularly important in that connection; and the tube 1 may still, if desired be made of glass, the grounded mem` ber consisting of a thin sheet metal shield laid against the walls thereof.

In case the tube be made of metal, however, especial care is requisite in sealing the same into .the wall of the globe although numerous expedients have been developed for effecting this as is well understood vin the art. For example the entire tube can be made of platinum which has the same coeflicient of 'expansion as soft glass andmis readily wet by the molten glass; or the tube may be made cf metallic tungsten which has appreciably the same coefficient of eXpanT sion as hard glass and can readily be sealed therein; or some special glass or enamel of the necessary characteristics can be interposed between the glass and the metal; or a collar 25 of some special metal like platibe either formed immediately on the exterior of the tube or onU the surface of a .sleeve which is slipped thereover as shown 1n Fig. 3, the latter arrangement being preferable in many ways as a manufacturingl expedient, regardless of the employment of any insulating layer 22. When made of metal this tube 1 is preferably itself very thin and hence more readily held in place vthan a thicker tube would be.

It will be understood that a great many changes 1n design and arrangements of part can be made Within the scope of my inven-` tive idea; and .that I do not limit myself to any form or arrangement whatever of grid, plate, or other operating elements; and that my improved tube, while designed for alternating current, can be operated with equal success on direct current of the proper voltage; and that in general I do not limit myself in any wise excepting as specifically set forth in my claim.

Having thus described my invention what I claim is:

In a thermionic tube, a globe, an impervious, thin-walled metal tube sealed therein, electronic emission substance on the side of said tube which faces the vacuum 'chamber, an electric circuit element connected to said substance, an electric resistance heating element in said tube, and a ground connection leading to a metallic part between said heating element and said emission sub-- stance.

In testimony whereof I hereunto affix my signature.

ORAN TMCILVAINE. 

